Most of the work was plug and play. Just needed a hack in to the reverse lights wiring to provide power and signal to a relay.
£29.99 for the Plug and play lead for Audio / Video in out from ebay.1p for the Camera plus £10.99 postage and £2 insurance.
Couple of hours tinkering and result! Works a treat in the dark too. In total darkness the rear fogs illuminate like football field floodlamps as it's an IR type camera.
Only pointer for anyone else who does this on a RRIII is that the '03 to '05 model needs an NTSC standard camera not a PAL for the reverse image, though convertors are available the camera is hardly going to break the bank.
My car is the RRIII Vogue which comes with the TV/Nav system (ala BMW styliee)
I've also got a spare Video input which I can use for a wireless cam mounted in the caravan. Result!
Lee D